Introduction. - Paraneoplastic Cushing's syndrome is a rare cause of endogenous hypercorticism. It is caused by ectopic secretion of ACTH by a non-pituitary endocrine tumor. The aetiological biological and radiological data are often inconclusive, which creates a problem of differential diagnosis with Cushing's disease. In addition, these tumors are often small and their location is extremely variable. As a result, the difficulties of localization require the use of specific imaging techniques.
Observation. - We report the observation of a 44-year-old man suffering from diabetes and high blood pressure, presenting a severe and rapidly progressive Cushing syndrome, in connection with a hypercorticism caused by an ectopic ACTH secretion. The thoracic computed tomography performed within the framework of a search for a neoplastic origin objectified a 15 mm nodule isolated at the level of the middle lobe, the scintigraphy with octreotide marked with indium-111 found a significant fixation at the level of the lung nodule. The patient had a middle lobe lobectomy. The outcome was favorable with regression of Cushing's syndrome. Pathological examination was in favor of a typical carcinoid tumor, and the immunohistochemical complement showed tumor cell positivity for ACTH, CD56, chromogranin, and synaptophysin.
Conclusion. - This observation illustrates the dilemma between the need to locate an ectopic ACTH secretion and the control of aggressive and threatening Cushing's syndrome. Early use of the octreotide scintigraphy should be considered if a topographic diagnosis of the causative tumor cannot be done through conventional imaging techniques.
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